/Engine/Source/Runtime/UMG/Public/Components/PanelWidget.h
Inserts a widget at a specific index. This does not update the live slate version, it requires a rebuild of the whole UI to see a change.
[UPanelSlot](API\Runtime\UMG\Components\UPanelSlot) * InsertChildAt ( int32 Index, [UWidget](API\Runtime\UMG\Components\UWidget) * Content )